1. Field of the Invention
The present invention relates to high power amplifier that is applicable for use in digital television systems using advanced silicon carbide transistor technology. More particularly, the present invention relates to intelligent high power amplifying modules, each of which includes a plurality of silicon carbide transistors and a dedicated hybrid controller for monitoring operational conditions within the module and optimizing the operational conditions to avoid unwanted failures. Even more particularly, the present invention relates to a high power transmitter which includes a plurality of independent amplification modules, each of which having a dedicated hybrid controller that monitors the status of a plurality of silicon carbide transistors of the module, adjusts the gain level of the amplifying module according to the status of the monitored silicon carbide transistors, and maintains the gain level of the module at a predetermined value.
The present invention relates further to a high power amplifier having a modular structure and includes a plurality of parallel-coupled silicon carbide transistors driven by a driving silicon carbide transistor, wherein the status of all silicon carbide transistors and the amplifier's temperature is monitored by a digital controller portion of the dedicated hybrid controller located within the module, for providing optimized operational conditions for both the amplifying module as the whole, and for each of the particular silicon carbide transistors of the output stage taken separately.
2. Prior Art
A wide variety of different amplifier circuits have been developed to provide high levels of power output. Silicon bipolar transistors incorporated in densely packaged structures which can handle kilowatts of peak power, are widely used in high power amplifiers and particularly in radio frequency transmitters. Disadvantageously, the silicon transistors cannot operate at relatively high operating temperatures, and therefore are typically operated below their rated power output capability in order to keep them within required operating temperatures. Additionally, the silicon transistors in high power applications have to be spaced apart from one another by relatively large separation distances for the same reason, thereby impeding further miniaturization of the amplifiers.
As the state of the art of high power RF transmitters (amplifiers) has advanced, there has been a demand that amplifying transistors used in RF transmitters handle more power, operate faster, be smaller in size and lower in cost. In response to these demands, scientists and engineers have developed static induction transistors capable of operation at high frequency and power and applicable for use in digital and analog television transmitters and in electric power conversion equipment. Static induction transistors are described in U.S. Pat. No. 5,705,830 and are constructed using silicon carbide as the semiconductor material. Silicon carbide is a wide energy band gap semiconductor which is an attractive material for the fabrication of integrated power circuitry, and which offers high saturation electron velocity, high junction breakdown voltage, high thermal conductivity, and a broad operating temperature range (around 500.degree. C.). The energy band gap and the maximum operating temperature range of silicon carbide is at least twice that of conventional semiconductors. The static induction transistors are constructed using silicon carbide as the preferred semiconducting material, offer improved characteristics which include higher breakdown voltage due to higher field strengths, lower thermal impedance due to better thermal conductivity, higher frequency performance due to higher situated electron velocity, higher current due to higher field before velocity saturation, higher operating temperature due to larger band gap, and improved reliability particularly in harsh environments.
Disadvantageously, despite the benefits of high power, high operating temperature and other improved performance characteristics provided by silicon carbide transistors, silicon carbide power modules of the prior art, fail to be provided with intelligence which should bring the RF amplifying module to a much higher level of quality and performance, allowing fault tolerance, quick fault isolation of the module, and optimization of operational conditions of the high power amplifying module.